New analytical methodology is to be developed to measure DNA adducts arising from occupational human exposure to ethylene, ethylene oxide, butadiene, styrene and propene. These chemicals were selected since they are widely used and genotoxic. Also they are anticipated to give the same types of DNA adducts. The proposed methodology basically comprises four steps: (1) isolate the DNA from a biological sample; (2) separate the DNA adducts from the bulk of the DNA; (3) electrophore derivatize the adducts; and (4) detect the electrophoric products by gas chromatography - electron capture negative ion-mass spectrometry (GC-ECNI-MS). Electrophoric derivatization/GC-ECNI-MS has been selected because of the need for sensitive, definitive measurements. Current methodology is limited in these respects, which makes it difficult to make accurate assessments of exposure and risk. It is important to measure DNA adducts in human samples. DNA is an ultimate target in the body for carcinogenic and mutagenic chemicals. Measurements of DNA adducts can help to sort out uncertainties arising from exposure of individuals to multiple chemicals, and from individual variations in metabolism and lifestyle. Our understanding of the biological significance of chemical damage to DNA is dependent on our ability to measure it.